Electronic nose sniffs chemicals with non-specific sensor arrays

NEWBURY PARK, Calif.-- After two years of beta testing and performance validation by the U.S. EPA, a company has an electronic nose which can sniff out a wide range of substances including volatile organic chemicals (VOCs).

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Instead of using physical sensors, the zNose™ (above) creates hundreds of virtual chemical sensors to identify the makeup of smells.
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NEWBURY PARK, Calif.--(BUSINESS WIRE) After two years of beta testing and performance validation by the U.S. EPA, a company has an electronic nose which can sniff out a wide range of substances including volatile organic chemicals (VOCs).

The highly reliable electronic nose, called zNose™, now is offered in commercial benchtop and handheld versions.

The first electronic nose technology to receive government validation from both the US Environmental Protection Agency (EPA) and the White House Office of National Drug Control Policy (ONDCP) was presented recently at the national meeting of the American Chemical Society being held in San Francisco's Moscone Center.

Dr. Edward J. Staples described details of the new device, called a zNose™, and the validation process by which it was tested to analytical chemists from around the world. Staples works as chief scientist and managing director of Electronic Sensor Technology, LP., the company which produces the zNose™.

Previous attempts by researchers and scientists to develop electronic noses, called eNoses, based upon non-specific physical sensor arrays, have failed to gain validation because the devices cannot be calibrated according to EPA or FDA methods, Staples said. But the zNose™ contains only a single patented sensor, a programmable gate array (PGA) to control the sensor and a directly-heated 1-meter long capillary chromatography column.

The device can speciate and measure the concentration of individual chemicals contained within odors and fragrances in 10 seconds. Instead of using physical sensors, it creates hundreds of virtual chemical sensors. It simultaneously creates high-resolution visual olfactory images, called VaporPrints™, which can be recognized by humans without any sense of smell.

The EPA validated the product for well monitoring and soil testing because it can quantify environmental pollutants. The electronic nose also can interface directly with GPS receivers and operate remotely over an Internet connection.

Although first developed for sniffing out drugs, explosives and environmental pollution, the instrument now is becoming popular with quality control users in the food, beverage, pharmaceutical and chemical processing industries, who now account for the majority of the company's customers. Sutter Home, one of the larger California wineries, now is using the product to quantify the concentrations of chemicals in wine.

The instrument can detect almost any vapor in the Volatile Organic Compound (VOC) group, explained Ken Zeiger, Director of Operations for EST. "As an example," he said, "if there is a well near a leaking gas tank, you would see the vapors of the gasoline in the water. If you are near a military base (such as Tinker AFB, Midwest City, Okla.) where degreasers are used, you may find TCE and PCE in the water."

How it works

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The zNose(TM) in use.
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The operator of the zNose starts by pulling a sample of air into a preconcentrator called a trap. Then he switches a valve connecting the trap to a capillary column. The trap heats very rapidly (in 10-15 milliseconds). This desorbes the analytes in the trap and launches the "package" of analytes into the column.

The different analytes go through the column at different times. When each analyte exits the column, it impinges on a quartz crystal called a Surface Acoustic Wave (SAW) device. The crystal becomes an oscillator operating at 500 Megahertz. As an analyte strikes the crystal, the frequency drops in direct proportion to its concentration.

This frequency shift translates to concentration levels as parts per million (ppm), billion (ppb) or trillion (ppt) depending on the strength of the analyte concentration. The SAW detector is an integrating detector so the developer differentiated this response to develop the chromatogram.

The instrument develops both the chromatogram and the VaporPrint™ simultaneously for display. Once the samples have been collected, the chromatogram and VaporPrints are developed in ten seconds. VaporPrints output directly from the detector and the chromatogram displays against a 360 degree polar plot of the chromatogram time (usually 10 seconds).

Since the trap is desorbed in about 10 milliseconds, the chromatograph displays discreet peaks separated by about 20 milliseconds. In a typical 10-second chromatogram, there are about 500 virtual sensor responses.

The product includes a Pentium multimedia laptop computer bundled with Office98, PCAnywhere and proprietary zNose™ software. The product comes ready to use upon shipment except for adding helium.

Electronic Sensor Technology (EST) is a limited partnership formed in 1995 between Amerasia Technology Inc. and Land and General Berhad, a blue chip corporation of Malaysia. Amerasia Technology Inc., a California R&D corporation, is responsible for inventing the zNose™ and is the general partner. The company currently has two issued and two pending patents.

Information on the company's technology and products can be obtained from the company Web site: http://www.estcal.com. Technical papers including the recent ACS2000 conference publication also can be downloaded from the Web site.

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